This invention relates to laser tools used in construction measurement and the use of laser beams to indicate reference lines and planes. In particular the invention relates to the remote pointing of a level laser beam toward an operator in the field. The invention also relates to pointing two reference laser beams which are at 90 degrees to each other in the horizontal planes as are commonly required in the construction industry. Laser instruments of this type project a beam or beams of laser light which indicate points along a level line. The invention consists of a self-leveling laser with a wide self-leveling range, a remote-controlled turntable, and a reflector carried by the operator used to call or page a reference beam to the operator.
In the simplest case, a laser projector is mounted to a carpenter's level and projects a laser beam parallel to the axis of the level. The spot produced by the beam striking a surface along the projected line indicates a point on the level reference line. This basic laser tool is described in Genho U.S. Pat. No. 3,897,637. In this case, the carpenter's level must be adjusted to level using the level vials on the instrument. In Rando U.S. Pat. No. 4,852,265, U.S. Pat. Nos. 4,912,851, 5,144,487 and 5,075,977, a self-leveling laser instrument is described which projects a level laser beam despite a tilt of the housing. A reference plane can be generated by rotating the self-level laser instrument about a point on a substantially horizontal surface. Since the height of the self-leveling laser instrument has not changed substantially during the rotation, every projected line is an element in the level plane.
Today, it is most common to generate the laser reference plane by projecting the laser beam into a rotating pentaprism. This technique is described in Studebaker U.S. Pat. No. 3,588,249, Aldrink U.S. Pat. No. 3,936,197, Rando U.S. Pat. No. 4,062,634, Rando U.S. Pat. No. 4,221,483, Borkovitz U.S. Pat. No. 4,993,161 and others. In all cases, the housing is fixed and a beam is rotated to generate a plane. Normally these instruments are mounted on tripods and require setup by the operator. The tripods are generally heavy and clumsy to carry and set up. Most of the self-leveling laser instruments require an adjustment base under the laser or on the instrument to adjust the base of the instrument to be within the self-leveling range. Most of these instruments have a self-leveling range of only 15 minutes of arc requiring some time to set up. This set-up time is costly for the operator. However, instruments with a self-leveling range of several degrees do not require adjustments for leveling and thus are more productive to use. Generally speaking, a rotating beam is too weak to see and a sensitive detector is needed. To locate the beam, the detector is manually raised and lowered in the beam to locate center, for establishing an elevation. A visual display on the detector or an audio tone indicates the beam position to the user.
The goal of the instruments described above and also of the present invention is to mark points at the same elevation or along a given line. When the beam is not rotating, the center of the spot may be marked with a pencil. When a detector is used, a reference notch on the detector guides the pencil mark.
It is sometimes common to point a stationary laser beam with the same motor which is normally used to rotate the beam continuously. In this way, the operator can mark desired locations within the job site without using an expensive detector. When the spot is visible on the wall, it is quickly and easily marked with a pencil. The disadvantage of this system is that the operator must move the beam to a new location for each point. This means he must walk back and forth between the instrument laser and the point to be marked. This is very time-consuming.
In the prior art shown in FIG. 1, a level plane may be established by positioning a self-leveling laser instrument 2 over a point and rotating the instrument as needed to mark points in the plane. Two beams 6 and 8 are projected from the housing at 90 degrees to each other. In this case, the operator must walk back and forth between the laser instrument and marking location to make each mark. This is time-consuming. The laser instrument is used to establish a building corner or other square feature used in construction.
In the laser marking system 20 shown in FIG. 2, a laser beam 22a may be moved to sweep to locations 22b-22d. Such pointing can be done manually or with a remote control device (not shown). The laser beam is rotated internally in the instrument, via a pentaprism 28 mounted on a housing 24 supported by a tripod 26.
In an alternate method of eliminating the detector, the visibility of a rotating laser is enhanced by scanning the level beam back and forth using the same motor which normally rotates the pentaprism. This product is marketed in the U.S. by Topcon. In this case a special target 30 with two reflecting stripes 32 and 34 is used. When a rotating laser beam 36 strikes the stripes, a signal is received within the laser instrument which reverses the motor drive current. The beam then scans repeatedly across the two stripes, which concentrates the beam making it more visible. Therefore the user sees the beam by eye instead of detecting it via electronic detector. The user can then mark an elevation or set an item at that elevation.
In the system of Hogan U.S. Pat. No. 3,790,277, shown in FIG. 4, a tripod-mounted laser instrument 40 rotates a measurement beam 42 by rotating the entire laser using a motor. An infrared transmitter 44 on a grade rod 46 emits a multidirectional light beam 48 which is received at the laser instrument 40. A receiver in the laser instrument detects the light emitted using a special directionally-sensitive receiver. In normal operation the motor rotates the laser instrument 360 degrees until the infrared signal is detected. The instrument then locks onto the infrared beam and tracks the signal as the operator moves about the field.
The instruments of the prior art are large and expensive. In addition they lack the versatility of a hand-carryable, self-leveling instrument, useful separately.